mirror of
https://github.com/MichaelGrafnetter/DSInternals
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309 lines
11 KiB
C#
309 lines
11 KiB
C#
// ---------------------------------------------------------------------------
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// <copyright file="Transaction.cs" company="Microsoft">
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// Copyright (c) Microsoft Corporation. All rights reserved.
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// </copyright>
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// ---------------------------------------------------------------------------
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// ---------------------------------------------------------------------
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// <summary>
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// </summary>
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// ---------------------------------------------------------------------
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namespace Microsoft.Database.Isam
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{
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using System;
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/// <summary>
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/// A IsamTransaction object represents a single save point of a transaction
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/// that is begun on a Session object. This object is not required to
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/// begin, commit, or abort a transaction as this can be done directly
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/// on the Session object. However, this object is very useful for making
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/// convenient code constructs involving transactions with the "using"
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/// keyword in C# like this:
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/// <code>
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/// using( IsamTransaction t = new IsamTransaction( session ) )
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/// {
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/// /* do some work */
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///
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/// /* save the work */
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/// t.Commit();
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/// }
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/// </code>
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/// </summary>
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public class IsamTransaction : IDisposable
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{
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/// <summary>
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/// The session
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/// </summary>
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private readonly IsamSession isamSession;
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/// <summary>
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/// The transaction level
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/// </summary>
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private readonly long transactionLevel;
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/// <summary>
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/// The transaction level identifier
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/// </summary>
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private readonly long transactionLevelID;
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/// <summary>
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/// The cleanup
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/// </summary>
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private bool cleanup = false;
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/// <summary>
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/// The disposed
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/// </summary>
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private bool disposed = false;
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/// <summary>
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/// Initializes a new instance of the <see cref="IsamTransaction"/> class.
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/// Begin a transaction on the given session.
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/// </summary>
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/// <param name="isamSession">
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/// The session we will use for the transaction.
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/// </param>
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/// <remarks>
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/// If this transaction is not committed before this object is disposed
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/// then the transaction will automatically be aborted.
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/// </remarks>
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public IsamTransaction(IsamSession isamSession)
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{
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lock (isamSession)
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{
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this.isamSession = isamSession;
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this.isamSession.BeginTransaction();
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this.transactionLevel = isamSession.TransactionLevel;
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this.transactionLevelID = isamSession.TransactionLevelID(isamSession.TransactionLevel);
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this.cleanup = true;
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}
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}
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/// <summary>
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/// Initializes a new instance of the <see cref="IsamTransaction"/> class.
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/// Joins the current transaction on the given session. If the session
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/// is not currently in a transaction then a new transaction will be
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/// begun.
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/// </summary>
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/// <param name="isamSession">
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/// The session we will use for the transaction.
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/// </param>
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/// <param name="join">
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/// If true, the current transaction on the session will be joined. If false or if there is no current transaction then a new transaction will be begun.
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/// </param>
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/// <remarks>
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/// If an existing transaction is joined, then committing or aborting
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/// this transaction will have no effect on the joined transaction. If
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/// a new transaction was begun then these actions will work normally.
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/// <para>
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/// If this transaction is not committed before this object is disposed
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/// then the transaction will automatically be aborted.
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/// </para>
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/// </remarks>
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public IsamTransaction(IsamSession isamSession, bool join)
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{
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lock (isamSession)
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{
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this.isamSession = isamSession;
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if (!join || isamSession.TransactionLevel == 0)
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{
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this.isamSession.BeginTransaction();
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this.transactionLevel = isamSession.TransactionLevel;
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this.transactionLevelID = isamSession.TransactionLevelID(isamSession.TransactionLevel);
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this.cleanup = true;
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}
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}
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}
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/// <summary>
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/// Finalizes an instance of the IsamTransaction class
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/// </summary>
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~IsamTransaction()
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{
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this.Dispose(false);
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}
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/// <summary>
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/// Gets the save point (level) for this transaction.
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/// </summary>
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public long TransactionLevel
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{
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get
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{
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this.CheckDisposed();
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return this.transactionLevel;
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}
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}
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/// <summary>
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/// Gets or sets a value indicating whether [disposed].
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/// </summary>
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/// <value>
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/// <c>true</c> if [disposed]; otherwise, <c>false</c>.
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/// </value>
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internal bool Disposed
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{
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get
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{
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return this.disposed || this.isamSession.Disposed || (this.cleanup && this.isamSession.TransactionLevelID(this.transactionLevel) != this.transactionLevelID);
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}
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set
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{
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this.disposed = value;
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}
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}
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/// <summary>
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/// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
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/// </summary>
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public void Dispose()
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{
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lock (this)
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{
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this.Dispose(true);
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}
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GC.SuppressFinalize(this);
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}
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/// <summary>
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/// Commits the save point (level) represented by this transaction on
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/// this session. All changes made to the database for this save point
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/// (level) will be kept.
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/// </summary>
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/// <remarks>
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/// Changes made to the database will become permanent if and only if
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/// those changes are committed to save point (level) zero.
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/// <para>
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/// A commit to save point (level) zero is guaranteed to be persisted
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/// to the database upon completion of this method.
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/// </para>
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/// <para>
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/// The transaction object will be disposed as a side effect of this
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/// call.
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/// </para>
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/// </remarks>
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public void Commit()
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{
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this.Commit(true);
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}
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/// <summary>
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/// Commits the save point (level) represented by this transaction on
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/// this session. All changes made to the database for this save point
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/// (level) will be kept.
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/// </summary>
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/// <param name="durableCommit">When true, a commit to save point (level) zero is guaranteed to be persisted to the database upon completion of this method.</param>
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/// <remarks>
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/// Changes made to the database will become permanent if and only if
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/// those changes are committed to save point (level) zero.
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/// <para>
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/// A commit to save point (level) zero is guaranteed to be persisted
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/// to the database upon completion of this method only if
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/// durableCommit is true. If durableCommit is false then the changes
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/// will only be persisted to the database if their transaction log
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/// entries happen to be written to disk before a crash or if the
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/// database is shut down cleanly.
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/// </para>
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/// <para>
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/// The transaction object will be disposed as a side effect of this
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/// call.
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/// </para>
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/// </remarks>
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public void Commit(bool durableCommit)
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{
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lock (this.isamSession)
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{
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this.CheckDisposed();
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if (this.cleanup)
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{
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this.isamSession.CommitTransaction(durableCommit);
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this.cleanup = false;
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}
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this.Dispose();
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}
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}
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/// <summary>
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/// Aborts the save point (level) represented by this transaction on
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/// this session. All changes made to the database for this save point
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/// (level) will be discarded.
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/// </summary>
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/// <remarks>
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/// The transaction object will be disposed as a side effect of this
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/// call.
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/// </remarks>
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public void Rollback()
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{
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lock (this.isamSession)
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{
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this.CheckDisposed();
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this.Dispose();
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}
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}
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/// <summary>
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/// Aborts the save point (level) represented by this transaction on
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/// this session. All changes made to the database for this save point
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/// (level) will be discarded.
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/// </summary>
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/// <remarks>
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/// The transaction object will be disposed as a side effect of this
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/// call.
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/// <para>
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/// IsamTransaction.Abort is an alias for <see cref="IsamTransaction.Rollback"/>.
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/// </para>
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/// </remarks>
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public void Abort()
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{
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this.Rollback();
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}
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/// <summary>
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/// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
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/// </summary>
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void IDisposable.Dispose()
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{
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this.Dispose();
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}
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/// <summary>
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/// Checks whether this object is disposed.
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/// </summary>
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/// <exception cref="System.ObjectDisposedException">If the object has already been disposed.</exception>
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internal void CheckDisposed()
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{
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if (this.Disposed)
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{
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throw new ObjectDisposedException(this.GetType().Name);
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}
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}
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/// <summary>
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/// Releases unmanaged and - optionally - managed resources.
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/// </summary>
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/// <param name="disposing"><c>true</c> to release both managed and unmanaged resources; <c>false</c> to release only unmanaged resources.</param>
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protected virtual void Dispose(bool disposing)
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{
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lock (this.isamSession)
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{
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if (!this.Disposed)
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{
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if (this.cleanup)
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{
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this.isamSession.RollbackTransaction();
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this.cleanup = false;
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}
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this.Disposed = true;
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}
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}
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}
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}
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}
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